Field of the Invention
The present invention relates to an electrophotographic member to be used in an electrophotographic apparatus, and to a process cartridge and an electrophotographic apparatus, including the electrophotographic member.
Description of the Related Art
An electrophotographic member is used for various applications such as a developer carrying member (e.g., a developing roller), a transferring roller, a charging member (e.g., a charging roller), a cleaning blade, and a developer layer thickness regulating member (e.g., a developing blade). It is preferred that such electrophotographic member have an electro-conductive property with an electric resistance value of about from 103 Ω·cm to 1010 Ω·cm. In Japanese Patent Application Laid-Open No. 2012-159807, there is a disclosure of the invention of an electro-conductive roller to be used mainly in a developing device. Specifically, there is a disclosure of an electro-conductive roller including an elastic layer formed on an outer peripheral surface of a mandrel and a urethane coat layer formed on an outer peripheral surface of the elastic layer, in which the urethane coat layer contains a urethane resin, at least one kind selected from the group consisting of a pyridinium-based ionic liquid, an amine-based ionic liquid, and an ionic liquid having two hydroxyl groups in an amount of from 1 part by mass to 25 parts by mass with respect to 100 parts by mass of the urethane resin, and a carboxylic acid-based metal compound in an amount of from 1 part by mass to 25 parts by mass with respect to 100 parts by mass of the urethane resin.
There is also a disclosure that according to such electro-conductive roller, both a charge-removing function of the electro-conductive roller on a developer under a low-humidity environment and a charging function of the electro-conductive roller on a developer under a high-humidity environment, which have hitherto been considered to have a trade-off relationship, can be achieved in a balanced manner.
The inventors of the present invention investigated the use of the electro-conductive roller of Japanese Patent Application Laid-Open No. 2012-159807 as a developing roller and found the following. A suppressing effect on excessive charging of a developer may decrease under a low-temperature and low-humidity environment such as one having a temperature of 15° C. and a relative humidity of 10%. As a result, in the case where the electro-conductive roller is used as a developing roller for forming an electrophotographic image over a long period of time, the developer is excessively charged, and a toner regulation failure occurs in some cases. The toner regulation failure may cause, for example, an image defect called a ghost or image defects such as dot-like unevenness in a non-printed portion and a toner lump formed on an image.
On the other hand, in the case where the electro-conductive roller is used as a developing roller for forming an electrophotographic image over a long period of time under a high-temperature and high-humidity environment such as one having a temperature of 32.5° C. and a relative humidity of 85%, the charged amount of a developer may become insufficient. Therefore, when a white solid image formed of a non-printed portion to which the developer is not allowed to adhere is output, the white solid image may be colored with the developer.